There has been a system in which enables online connection of an image forming apparatus such as a copying machine to a controller installed at a site such as a service center making use of the public line network. This system provides centralized control over a plurality of copying machines installed at remote sites with a host machine installed at a site and uses the data obtained from the copying machines for collecting data for usage of each copying machine or for maintenance of each copying machine. As contents of the maintenance, such operations as an automatic call from a self diagnosis function in a copying machine to a controller or adjusting each section of a copying machine by accessing each copying machine from the controller are executed. Also in the past, a count (generally a number of sheets of copy paper) for accounting to a customer in relation to the maintenance contract for a copying machine usually checked by way of visit by a service engineer to the customer or calling the customer through a telephone system has been read by means of remote operation using the above system.
Furthermore there has been proposed a system constructed so that, when transmitting data concerning each copying machine through the public line network to a controller, if it is impossible to transmit the data because, for instance, another system occupies the line, transmission of data is automatically retried up to a previously specified number of times to transmit data.
As the reference technological documents concerning the conventional technologies as described above, there are, for instance, Japanese Utility Model Laid Open Publication No.100561/1989 disclosing the "copying machine allowing remote and automatic inspection of a meter through a telephone", Japanese utility Model Laid Open Publication No.100562/1989 disclosing the "network control system for automatic inspection of a meter of a number of copy paper", and Japanese Utility Model Laid Open Publication No.103950/1989 disclosing the "copying machine allowing remote and automatic inspection of a meter through a telephone".
In addition, as a system in which various types of data concerning a copying machine are transmitted and received, there is the "system for collection of data concerning an image forming apparatus" disclosed in Japanese Patent Laid Open Publication No.257155/1990, and furthermore as a system for periodically transmitting data for a copying machine, there is the "system for collection of data concerning an image forming apparatus" disclosed in Japanese Patent Laid Open Publication No.259666/1990. Furthermore as a system for receiving a remote control signal through a communication line and executing processing according to the remote signal, there is the "image forming apparatus" disclosed in Japanese Patent Laid Open Publication No.196053/1991.
In the conventional systems as described above, however, times for recall are limited, for instance, to 5 times, and at a point of time when the fourth recall is finished, if new data to be transmitted is generated, only one opportunity for recall is given even to the new data together with the old data, and the recall function is inappropriate for transmitting the new data.